[91.14] Using the Milky Way to Test a New Alternative to Newtonian Gravity

D. F. Bartlett (University of Colorado at Boulder)

The evidence for dark matter (and dark energy) is powerful,
but not yet overwhelming. I propose an alternative that -
like Yukawa's potential - allows scalar gravity to obey a
second order linear differential equation. Consider the
sinusoidal potential \phi(r)=-(GM/r) cos(kr). Here
\lambda=2\pi/k is a universal wave length which -- judging
from evidence both from within the Galaxy and without -- is
Ro/20 or about 425 pc. For r = 1 AU, cos(kr) differs
from 1 by only 10-14, too small a difference to have
been detected in the motion of the planets. Alternatively,
if kr>1, the sinusoidal potential provides both a
gravitational force and a tidal force which diminish only as
1/r. The slow decline in force can explain the flat
rotation curves of stars in disk galaxies.

It is, however, the very strong tidal forces that provide
the real evidence. There is unexplained modulation (of
period \lambda) in our Galaxy. This is seen in both
Burton's (1988) profile of the H I layer and in the study of
CO velocities by Clemens (1985). Closer to home, Matese and
Whitmire (1997) have found that the perihelia of long-period
comets are influenced by the galactic tidal force to a
surprisingly large extent. The surprise can be removed if
the tidal force is kRo = 120 times greater than expected.
Strong tidal forces also appear to be responsible for the
hierarchy of galactic structures: bar, extreme disk, thin
disk, thick disk, and halo.

I will also answer general questions such as: Why do disk
galaxies resemble spirals rather than Saturn's rings? Is
there a link with quantized red shifts? Can the proposed
potential predict which galaxies have central black holes?